Help again!!

[Stephanie Hanna]

Hi everyone, this is Stephanie again. A lot of you helped me about a month ago when we bought a 2002 NX 750 with a 135 Optimax on it. We couldn't get on plane. We thought we had it but that must of been a one time episode. We have been trying forever and my husband is becoming very frustrated . He has never had trouble driving a boat.We kinda of look like newbies out ont he water. MY husband went to a dealer yesterday to buy a hydrofoil and this dealer said that is kind of like a quick fix and doesn't address the real issue. Also, reading what all of you have said about being careful in turns with it, I am a little leary. This dealer said we need to go down in pitch. It is a Trophy Plus 4 blade 23p right now. All holes are open. No plugs.A new prop is going to cost 400-500 dollars. He said his mechanic could re-pitch it for 150.00. My husband then called the Nitro company, they also said to go down in pitch because as a motor ages , it loses performance. I went on the Mercury site as Teri suggested and put in motor and performance of boat. They listed the prop that we have but nothing was less than a 25p up to 27p depending what we wanted out of the boat. NOW we are really confused. We don't want to spend money to re-pitch is it isn't going to work. We don't care about top speed, we just want out of the hole. We have done everything that was told to us earlier, ex. trimming down all the way first, getting up some momentum and then taking off, then trimming up as we go. NOTHING. Max RPMS seem to be around 6000 and speed around 62. We also porpoise really bad at speeds of 30-40. We know this is an awesome boat if we can just get it tuned in. ANY help at all would be very appreciated!!

Thank you

Stephanie

 

[Brian Ingersoll]

It sounds like you need to go up in pitch, not down to get your rpm's in the recommended range, but that will hurt your holeshot even more. I don't remeber all of the previous posts, but have you tried pulling the PVS plugs out of the prop one at a time.

You used to be able to go to select Mercury dealers and get a loaner prop to try out and see if it works. I beleive their website has a search function to find participating dealers. If I remeber right the props are painted blue.

 

[Rusty Williams]

If u are turning 6000 rpm the prop u have is fine. Lower pitch will cause an increase in hole shot and RPM but 6000 rpm is about what the right size prop should allow. I think the issue is deeper in the engine. I don't know about an Opti but i know the older motors had coils on each cylinder that could go bad causing loss of spark in a cylinder thus causing a miss which would rob u of mose all of your power getting out of the hole but still allow it to make full RPM after a small time. Get your motor checked for cylinder miss.

 

[Rusty Williams]

Also check all gas lines to see if u have a pin hole in a line which will cause the system to *suck air* when in a high fuel demand situation. That will cause the engine to starve for fuel when u are trying to get onto plane. I think i would take it to a dealer who has the equipment to plug into the motor to tell u what's wrong but i am quite sure it isn't the prop and it doesn't need a *fin* to make it power up properly.

 

[Edward Rose]

Stephanie plug the holes in your prop.

 

[Jim B]

It sounds to me like Ed is on the right track, you may have too much venting causing the prop to slip too much. What are your rpms when you bury the throttle on takeoff? You may need to plug the holes or geta cavitation ring for the prop or both.



Another thing is the 4 blade prop itself. I tried a trophy and a tro4 on my nx 882 when I had it and both were just all wrong on that hull, the holeshot was awful using that prop. You may want to try and borrow a 23 tempest plus and try that out. You may find that prop will be perfect.



The foil should not be needed on that combo at all. You are not remotely underpowered so the foil would just be a band-aid for a setup issue.

 

[Greg Duggan]

I run a 23p Tempest Plus (this is a 3 blade prop)on my 135 Opti, i have a NX882 wich is slighty bigger and heavier. I have all three plugs are in, not sure of the size plug but i can get the number off them if you would like.

If the 135 opti can get my boat on plane quickly, then it should blast the NX750 out with no problem at all.

If you have the oportunity to try a tempest before you buy it, i think it will help you out quite a bit. to bad your not in the north east i would be happy to give you my prop to try out. ask around and maybe some one can accomidate this for you.



GregD

 

[Mini]

Look on the Mercury website for a dealer near you that has loaner props. Do some testing with pitch before you decide what to do.



Some of this could be from how the boat is loaded too.

 

[Tom Jones]

Did I miss something or didn't the dealer say the hydrofoil would "fix" it??:blink:

And what the heck is a "quick fix??" I can put it on in ten minutes and you are fixed?!?:huh::wacko::blink: For that matter, you could put it on yourself. It's not like it will work for a few trips and then all of the sudden not work for some reason!:huh: Since you have no concerns about top end speed and assuming the engine is running good, try the loaner prop method if you can to see if you can find a better prop,if not, then add the hydrofoil if it still is not suitable enough holeshot for you. The addition of a foil an my boat made ALL the difference and no prop change was made.

 

[Cliff Van Beek]

OK one of the posts may give some lead into the real issue.....when hammering down, what do the RPMs do? is it blowing out and over reving, then you need plugs, i agree 6000 top rpm is almost too fast, it is likely a 5600 RPM engine, i just put a 250 on my 911, and have been playing with props, with the 25 tempest i removed all the plugs....bad move, blows out bad.....one other thought, is if the prop has been ran in a sandy area, the cup will dissapear, it could be damaged enough to take away hole shot and top end hold......find the dealer with loaner props and play, most good dealers have them and will let you use them to sell product.

 

[TROY WAINRIGHT3]

Stephanie,Ive ran across this many times.Forget the hydro foil.If your motor is running 6000 rpms then nothings wrong with the motor.Your quick fix is like ed said.CHEAP prop plugs.Get the large,medium,and small plugs and experiment with them.Ive got a laser prop on a 150 pushing a 20 foot no problem.All 3 holes have med. size plugs in them.Good luck and let us know what ya find.

 

[FLsportsman]

I agree with rw; check engine performace. I'm dealing with poor engine performace which reflects in my hole shot.